Assessment of UV-activated persulfate process for the degradation of parabens and its degradation product p-hydroxybenzoic acid in environmental matrices

Abstract

In the present study the simultaneous degradation of methyl paraben (MeP) and propyl paraben (PrP), as the most often used parabens, as well as its major transformation product p-hydroxybenzoic acid (p-HBA) by UV-C/PS in different aqueous matrices was investigated. The effects of various parameters such as the initial oxidant concentration, solution pH, humic acid content and inorganic anions on the efficiency of the process were evaluated. The degradation pathways were also evaluated through the assessment of the role of the reactive radicals as well as the identification of the transformation products. Moreover, the toxicity evolution during the process was estimated using two different microalgae species, i.e. Scenedesmus rubescens and Dunaliella tertiolecta. UV-C/PS was effective to degrade all the studied contaminants in all the aqueous matrices that is correlated with the formation of the reactive radicals HO· and SO4·−. However, the organic and inorganic content that co-exist in lake and drinking water as well as wastewater significantly affected the rate of the removal. The degradation was found to proceed through hydroxylation and ring opening reactions. The process was also found to proceed without the formation of compounds of concern. Moreover, UV-C/PS process had a positive effect on transferring toxic organics and inorganics to harmless compounds and was able to significantly reduce the toxicity of the wastewater.